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Mercury is currently located on the far side of the Sun. The innermost planet passes through superior conjunction on February 16th. Throughout the month it remains too close to the Sun to be safely observed.

Venus

Venus returns to the evening sky for the first time since March 2017. The brilliant planet shines at mag. -3.9 and can be seen during twilight from northern locations, very low above the western horizon towards the end of month. However, those living further south will struggle to spot the planet.

Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.

Why the brightness change. The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.

Dwarf planet Ceres, the largest object in the asteroid belt, reaches opposition on January 31st. It will peak at magnitude +6.8, as it moves retrograde in Cancer. Bright stars Castor (α Gem - mag. +1.6) and Pollux (β Gem - mag. +1.1) in Gemini can be found about 20 degrees further west. Since Ceres travels quickly with respect to the "fixed" background stars, it can be tracked on a nightly basis. Although Ceres is too faint to be spotted with the naked eye, it's easily visible with binoculars and small telescopes. In addition, this opposition is very favourable as this dwarf planet peaks close to its maximum possible brightness. At opposition, it will be 1.602 AU (approx. 239.7 million kilometres or 148.9 million miles) distant from Earth.

Variable star Mira (omicron Ceti - ο Ceti) is now close to peak magnitude and for the next couple of months will be visible to the naked eye. This popular variable star, also known as "the Wonderful", is located in the constellation of Cetus. It can be seen as soon as it's dark enough, towards the south from northern locations or towards the north from southern locations, and remains visible until around midnight.

Mira's peak magnitude is expected to be about +3.4. The star climbs very quickly from minimum to maximum brightness over a period of about a month and then takes a quieter route on the downward slope, requiring 6 months to reach minimum. The minimum magnitude is usually of the order of +9, when at least a pair of binoculars and dark skies will be required to spot it.

The first annual meteor shower of the year is the Quadrantids and it can be a good one with up to 60 meteors per hour visible at peak time. This rate is comparable to the much observed Perseids and Geminids, but unlike these showers the Quadrantids are elusive with a narrow peak activity window lasting just a few hours. Unfortunately, this year's event is not favourable. The Moon, just past full, will significantly interfere and therefore wash out all but the brightest meteors.

Radiant and History

Meteor showers are usually named after the constellation that contains the radiant, but you will have difficulty figuring out the relevant constellation for the Quadrantids. The reason is it no longer exists. Today, the Quadrantids radiant is located in Boötes, not far from the tail of Ursa Major. When the shower was discovered in the 1830s by Adolphe Quetelet of the Brussels Observatory the radiant was located in the now obsolete constellation of Quadrans Muralis, hence the name "The Quadrantids".

Mercury reaches greatest elongation on New Years Day when it moves out to 22.7 degrees west of the Sun. The innermost planet can be seen just before sunrise during the first two weeks of the month, low down above the south-eastern horizon. During this period its brightness is fairly constant at magnitude -0.3, with its illuminated phase increasing from 62% to 85%.

Mercury passes less than a degree south of Saturn on January 13th. Two days later the thin waning crescent Moon passing 3 degrees north of Mercury.

Venus

Venus passes through superior conjunction on January 9th. It remains too close to the Sun to be safely observed throughout the month.

Earth

Earth reaches perihelion or closest point to the Sun on January 3rd at a distance of 0.983 AU or 147.1 million kilometres (91.4 million miles).

Mars

Mars is now an early morning object. Except for a few hours on the last day it spends all of the month moving south-easterly through Libra. The planet increases in brightness from magnitude +1.5 to +1.2, with its angular diameter improving slightly from 4.8 to 5.6 arc seconds as the month progresses.

Mars never strays very far away this month from much brighter Jupiter (mag. -1.9). On the morning of the 7th, the two planets are at their closest and positioned less than 0.5 degrees apart. However at magnitude +1.4, Mars is about 20 times fainter than Jupiter.

Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star", most of the time it shines at mag. +2.1 but every two days, 20 hours and 49 minutes it suddenly dips in brightness to mag. +3.4, remaining dim for about 10 hours before returning to its original state.

Why the change in brightness? The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary, resulting in a very small dip in brightness that can be detected with photo-electrical equipment.

The major meteor event in December is the Geminids but there's another shower later in the month, the Ursids, that doesn't make as many headlines but on occasions can be quite good. With the radiant located close to the north pole star, the Ursids are a northern shower. They are nowhere near as spectacular as the Geminids, but on occasions have shown significant bursts of activity and a re-occurrence may occur any year.

This year, the shower peak occurs on the night of December 22 / 23 and the four day old waxing crescent Moon won't significantly interfere.

The Geminids or "Winter Fireworks" is widely regarded as the richest and most active of the annual meteor showers with this year's event peaking on night of December 13th/14th. During peak activity up to 120 meteors per hour can be seen under perfect conditions, including many bright ones. Of all annual showers, only the Perseids comes close to attaining such highs. This year's event promises to be a good one as the waning crescent Moon won't interfere. It may even be extra special as the parent asteroid, Phaethon, passes close by the Earth during the activity period.

Parent asteroid

The Geminids are unusual in that the source object is an asteroid, 3200 Phaethon. Together with the Quadrantids, they are the only major meteor showers not originating from a comet. Phaethon has an orbit that brings it closer to the Sun than any other named asteroid, although there are several unnamed asteroids that do approach closer. At perihelion - the point of closest approach to the Sun - it's only 0.14 AU distant and much closer than the innermost planet, Mercury. However, at aphelion (the point of furthest distance from the Sun) the asteroid moves out to 2.4 AU, and therefore beyond the orbit of Mars.